It is desirable that the hub cushion of a steering wheel serves as the operating button for the horn of a motor vehicle in spite of the presence of an airbag in the steering wheel. For this reason, driver's side airbag modules until now often have been assembled onto a horn mechanism arranged in the steering wheel, so that the entire airbag module serves as an operating button for the horn.
Such an arrangement of an airbag module is known, for example, from U.S. Pat. No. 5,650,600. In this arrangement, the airbag housing, which houses the gas generator and the folded together airbag, is fastened on two resilient members by means of a plurality of bolts. Insulating members are arranged between the resilient members and the airbag housing to insulate the resilient members electrically from the airbag housing. Furthermore, insulating members are provided between the bolts, by which the airbag housing is fastened on the resilient members, and the resilient members, in order to prevent electrical contact between the bolts and the resilient members. The bolts are threaded into the airbag housing from the underside and are connected to the housing in an electrically conductive manner. The bolt heads are designed as contact pins. The resilient members are welded to a contact plate, which is fastened on the steering wheel by means of threaded fasteners. The horn of the motor vehicle is operated by exerting pressure on the front panel of the airbag module and consequently on the airbag housing. Thus the resilient members are elastically deformed and the bolts designed as contact pins come into contact with the contact plate. In this way, an electrical connection between the airbag housing and the contact plate is established, which closes the horn circuit and consequently puts the horn into operation.
A further arrangement of an airbag module in combination with a horn mechanism is known from EP 0 572 125. Here, between the airbag housing and a support bracket provided on the steering wheel there are arranged compressible members that permit a resilient movement of the airbag housing in the direction of the support bracket. The airbag housing is fastened on the support bracket by means of threaded bolts, which are electrically insulated from the support bracket by additional insulating members. These bolts serve as guiding members, along which the airbag housing and support bracket can move toward each other. When there is pressure on the airbag housing as an operating button for the horn, the airbag housing and the support bracket are brought into contact with each other, whereby the horn circuit is closed and the horn is activated.
These known arrangements of an airbag module in combination with a horn mechanism all comprise a multiplicity of parts and require diverse additional insulating members. Furthermore, assembly is laborious and time intensive, since numerous threaded fasteners are employed. Assembly is additionally made more difficult by the fact that the required threaded fasteners are arranged in such a way that they are poorly accessible, so that assembly is difficult and consequently also time-intensive and expensive. The large number of parts required results not only in the additional costs for the parts but also in increased costs for storing and providing them.